One of the few movies legendary film critic Roger Ebert admitted to walking out on (during the Brothel-Boat orgy sequence), calling it "sickening, utterly worthless, shameful trash. If it is not the worst film I have ever seen, that makes it all the more shameful: People with talent allowed themselves to participate in this travesty." He reviewed what he saw, giving it zero stars, and ended with a quote from another viewer who told him "This movie is the worst piece of shit I have ever seen."

A whopping $7.50 (seven dollars and fifty cents U.S.) was the first-run admission price at its US premiere, at the Penthouse East Theatre, New York City in 1980. Average prices of movie tickets back then were around $3.

Tinto Brass originally wanted to cast actual criminals in conditional sentence as the Roman senators and ugly women in the sex scenes to shock the viewers. Because of this, Bob Guccione fired Brass of the production.

After the film was released, Anneka Di Lorenzo (aka Marjorie Lee Thoresen, a 1975 Penthouse Pet of the Year), who played Messalina, sued Bob Guccione, saying that his handling of the film, mainly his adding of the hardcore sex inserts, had damaged her acting career by associating her with a hardcore porno film. She won her case, but was awarded only $4.06 (four dollars and six cents, U.S.) in damages.

Under the supervision of Danilo Donati, 3592 costumes were designed. The cast wore 5000 handcrafted boots and sandals. The wigs were made from more than 1000 pounds of human hair, which was painstakingly sorted and matched.

The movie was originally set to be a low-budget historical drama film by Gore Vidal and his friend's nephew Franco Rossellini. When both saw that they could not make the film with a extremely low budget, Vidal contacted Bob Guccione for help. Guccione agreed so as long as the movie was included with hardcore sex and nudity to promote his adult magazine. Vidal and Rosselini didn't like the idea at first, but Vidal had promised TIME Magazine to make a movie adaptation of his 1972 screenplay, so they both agreed.

The film opened at #1 in the Box Office in both Italy and US, grossing $20 Million in a week, until it was removed from theatres due to public petitions. According to Bob Guccione, it would have entered in box office history if it wasn't removed.

Maria Schneider was originally supposed to play Drusilla and actually started shooting some scenes, but she changed her mind while filming a sex scene with Malcolm McDowell. Deeply disturbed by her skimpy toga and the graphic incest scenes, she walked off the set bad-mouthing the production.

Malcolm McDowell later reminisced how his car was attacked by a mob of angry extras and production assistants when he arrived on set because no money came in from New York to pay their weekly salary. Only after Carla Cipriani led a strike that delayed the production, did cast and crew finally get paid.

An ad in the Wednesday 28 July 1976 issue of Variety, announcing that filming was to begin that day in Rome contained the words, "What better proof that I am God. I have a husband. And a wife. I am all that is and shall ever be." However, when the film was finally released three years later, after numerous re-writes and re-edits, no mention of Caligula's husband, let alone his much reported homosexual tendencies, was included in the final product.

Despite popular beliefs, Gore Vidal and Tinto Brass did not disown this film because Bob Guccione inserted hardcore sex and graphic violence sequences and changed the point of the film. In reality, only five or six minutes of the 156-minute version of the film was part of Guccione's reshoot - that five or six minutes consists of the lesbian tryst in the secret room, and several inserts in the imperial bordello scene. Everything else was shot by Brass. Vidal disowned the film because Brass and lead actor Malcolm McDowell changed the point of view of his screenplay. Brass disowned it because Guccione locked him out of the editing room (some in the industry suspect it was because Brass didn't want to use Guccione's hardcore inserts) after assembling the first 40 minutes (which was probably disassembled shortly afterward). Guccione then proceeded to edit the film himself, but he often chose shots that were never meant to be included (the many zooms, out-of-focus shots, etc.), and also cut up certain scenes and put them in the wrong order. A prime example of this is Caligula's nightmare scene with Drusilla, which now occurs in a part of the film that would have been quite impossible dramatically, and is actually the first half of an earlier scene, which occurs just after the credits (together, the two scenes were meant to be the opening of the film, and the current opening in which Caligula and Drusilla enjoy a romp through a forest was intended for an entirely different purpose altogether, and was meant to occur much later).

When Nino Baragli and Bob Guccione cut the film together, several scenes were truncated and cut into the film in a seemingly random order. A few examples of scenes made fragmented in editing:

The opening is a fragment of a scene that was meant to occur immediately following Tiberius's death (this is why Caligula is clean shaven in this scene, but has a beard in the next). It was supposed to depict Caligula and Drusilla enjoying their new freedom as they no longer need to worry about being seen by Tiberius's informers. The scene is almost certainly shorter than it was intended to be, and thus is now a meaningless fragment.

The scene that was meant to be the opening is cut in half and moved around. In the final cut, the first half of this scene (which depicts Caligula worrying to Drusilla about Tiberius killing him) occurs between Caligula's tour of the grotto and Nerva's suicide. The second half of the scene (where Caligula and Drusilla fool around and are caught by Macro) now immediately follows the opening credits.

When Caligula and Nerva walk down the path to Tiberius's pool, we can hear people being tortured behind a curtain, which Caligula looks through at one point. The fragments of people being tortured several scenes later were meant to be intercut with the scene of Caligula and Nerva in the hall. Also, several scenes later, we see bodies being taken off crosses and servants clearing the pathway. These were meant to act as establishing shots for the scene in the hall.

Mixed in the scene on Tiberius's pleasure grotto are shots of an orgy, some of which filmed through mirrors. It's unclear what the purpose of these shots were, but they were obviously not meant for this scene (as they take place in a different room, and, thus, are cutaways to a location across the palace).

In the scene where Caligula, Caesonia, and Drusilla have sex, the movie includes inserts of a lesbian tryst that was one of the extra scenes shot by Bob Guccione. This footage replaces shots that made this scene necessary for the plot (the original concept had the palace informers looking through the peephole, thus explaining the closeups of the moon face in the bedroom), as well as a different lesbian act featuring the ladies-in-waiting, shot by Tinto Brass.

The shot of Caligula being scared by a black bird while playing with a rat was originally part of a much longer scene in which he sets up many small chariots for a race to entertain his daughter, and, thus, was also meant to be included somewhere in between the I am God scene and the imperial bordello scene (along with several other cut scenes (such as the sacrificial scene and the scene where Caligula claims himself to be king of the gods) and relocated scenes (such as Proculus's death)).

The opening credits are shown over a gold coin representing the laureate head of Caligula looking left and weeping tears of blood. This was a promotional image coined by the producers and used extensively in posters, based on the orichalcum sestertius (a league of gold and other metals) that was struck in Rome in AD 37-38, to commemorate Caligula's ascension to power and his address to the Praetorian Guard.

Contrary to the popular beliefs, the infamous 210 minute pre-release version of the film never existed. The mix-up came from an erroneous film program printed for the first public screen of "Caligula" at the Cannes Trade Festival (not to be confused with the Cannes Film Festival that occurs around the same time of the year) that stated that the entirety of the "Caligula Screening" runs 210 minutes. What it forgot to say, however, was that both the film (in its 156 minute edition) and the one hour making-of featurette were shown back to back that night, thus creating the three and a half hour running time.

On his way to the set, Malcolm McDowell encountered John Gielgud, who asked him if he'd seen the set. When McDowell replied that he was on his way there, Gielgud said, "Oh, it's wonderful. I've never seen so much cock in my life".

In the original conception, three men were seen talking and bathing in red mud. They are startled when Caligula first appears in the hallway outside Tiberius's pool. As Caligula walks down the hall, we see fragments of tortures that occur on the other side of the curtain. In the movie, the scene with the three men was moved *after* Nerva's death, and entirely new dialogue was dubbed over the shot, making it appear that the men are discussing Nerva's recent death and Tiberius's imminent death. They appear to be startled, then there is a cut to Caligula across the palace, fantasizing about torture, intercut with the fragments of tortures that were meant to be about 15 minutes earlier in the film.

Unused bits from the scene where Chaerea, Longinus, and a few senators discuss the possibility of Caligula dying from a fever were used to build a new scene toward the end of the film where (it appears) the men plot Caligula's murder. Almost all of the dialogue in this scene was invented in the dubbing stages, and most shots obscure the mouths of each speaker.

The principal cast members agreed to do voice re-recording sessions only if Bob Guccione's inserts would be left out of the final cut. He obliged, and the actors worked with a cut of the film that was free of the six minute re-shoots. However, once they were done, Guccione proceeded to add the inserts back into the film.

Several different versions of the film have been circulated: - Caligula was originally released in the UK with a running time of 149 minutes, with the hardcore sex replaced by alternate footage inserted by the distributor. However, the latest UK release (and now legal version) has a PAL running time of 98 minutes, 34 seconds (approximately 102 minutes film/NTSC), and is the same as the older R-rated version in the USA. The original 149 minute cut is now highly sought-after. - A 105 minute R-rated version was released in the USA in 1981. This version also used alternate footage and angles in the hardcore sex scenes and during scenes of graphic violence. - The official "uncut" version runs at 156 minutes and includes about six minutes of re-shoots by Bob Guccione. - In 1984, the film was re-cut and re-released in Italy under the title Io, Caligola. It ran 133 minutes, and was cut to 123 minutes by the Italian censors. When released on home video, some of the hardcore footage shot by Bob Guccione were reinserted into the film. - The second (and current) R-rated version was released in 1999 and used no alternate footage or angles, with the same shots repeating several times to mask the cuts in the film. The rumors of a 210-minute version screened at the Cannes Film Festival in 1979 are untrue - see note below.

According to a Tinto Brass interview both Maria Schneider and Isabelle Adjani tested for the role of Drusilla. Schneider won the role but left the production after a few days filming, due to an argument over the amount of nudity revealed in her costume during Tiberius's funeral scene.

Gore Vidal's screenplay had a strong focus on homosexuality, leading Bob Guccione to demand rewrites which toned down the homosexual content for wider audience appeal. Guccione was concerned that Vidal's script contained several homosexual sex scenes and only one scene of heterosexual sex, which was between Caligula and his sister Drusilla

Peter O'Toole did not endear himself to Bob Guccione when he told the producer that he planned to launch his own magazine to rival Penthouse. It was to be called Basement and would include such features as 'Rodent of the Month' and 'Toe Rag of the Year'.

During the film's production, Malcolm McDowell took members of the production to dinner at an expensive restaurant to celebrate England's win in a football match against the Italian team. He left the choreographer to pay for the meal, saying he had forgotten to bring enough money.

According to Malcolm McDowell, while filming the scene where Tiberius stabs a drunken soldier, Peter O'Toole was supposed to ram this sword into a concealed rubber bladder that contained blood, wine and chicken gizzards to look like a man's innards. He placed the sword under the plate and snapped it up with such force, it hit the actor in the face and knocked him out. But the sword didn't pierce the bladder and the goat skin, with all the wine and gizzards literally bounced a few times. Then O'Toole quipped, "I think she's dropped her fucking handbag!"

The film was a hit at the box office when the number of theaters it played in is taken into account. However, because of its limited run, it was a financial disappointment when compared with the more successful films of the time, even though it broke records in the individual theaters it played in. It since has gone on to become Penthouse's best selling video.

Orion Pictures was offered to pick up the film at the suggesting of its distribution partner, Warner Brothers. Film producer Mike Medavoy was an executive at Orion, and in his book "You're Only as Good as Your Next One," he recalled that he and another studio head were offended with what they saw. The producer of "Caligula" knew it, and all he could say to the executives is if they liked the art direction. "You bet we did," wrote Medavoy, "But that was about all we liked."

A Madison, Wisconsin district attorney declined an anti-pornography crusader's request to prevent the release of the film on the basis that "the most offensive portions of the film are those explicitly depicting violent, and not sexual conduct, which is not in any way prohibited by the criminal law."

Atlanta, Georgia prosecutors threatened legal action if the film was to be screened in the city, but experts testified in court on behalf of the film, and Atlanta, too, declared that the film was not obscene.

Because the film was intended for release in English and much of the dialogue was recorded in Italian, the film's soundtrack had to be looped. Peter O'Toole was reluctant to re-record his dialogue. He was kept away from the film's producers until he re-recorded his dialogue in a Canadian recording studio.

In 1979, when Bob Guccione tried to import the film's footage into the U.S., customs officials seized it. Federal officials did not declare the film to be obscene. When the film was released in New York City, the anti-pornography organization Morality in Media unsuccessfully filed a lawsuit against these federal officials.

Citizens for Decency through Law, a private watchdog group which protested against films which it deemed immoral, sought to prevent the film's exhibition in Fairlawn, Ohio on the grounds that it would be a "public nuisance", leading Penthouse to withdraw the film from exhibition there to avoid another trial. CDL's lawyer advised against attempting to prosecute Penthouse for obscenity and instead recommended a civil proceeding, because the film would not be placed against the Miller test. The Penthouse attorney described the Fairlawn events as being driven by conservative morality reinforced by Ronald Reagan's presidential victory, stating, "Apparently, these extremists have interpreted a change by administration to mean a clarion call for a mandate to shackle the public's mind again."

At the end of the production, Malcolm McDowell gave his dresser a pendant bearing her name, but it was misspelled and she gave it back to him. McDowell offered her a signet ring, a prop from the film. She refused because it belonged to the production company.

Art director Danilo Donati had to scrap some of his more elaborate original ideas for the sets and replace them with such surreal imagery as bizarre matte paintings, blacked-out areas, silk backdrops and curtains. This resulted in significant script changes, with Tinto Brass and the actors improvising scenes written to take place in entirely different locations, and sometimes shooting entirely new scenes (such as the frolicking scene that opens the film) in order to show progress while the incomplete or redone sets were unavailable.

Bob Guccione chose Tinto Brass to direct after being impressed with Salon Kitty (1976). When Brass was hired, he was in the middle of lawsuit to prevent that film from being released in an edited version.

In Boston, Massachusetts, authorities seized the film. Penthouse took legal action, partly because Bob Guccione thought the legal challenges and moral controversies would provide "the kind of [marketing] coverage money can never buy". Penthouse won the case when a Boston municipal court ruled that the film had passed the Miller test and was not obscene. While the Boston judge said the film "lacked artistic and scientific value" because of its depiction of sex and considered it to "[appeal] to prurient interests", he said the film's depiction of ancient Rome contained political values which enabled it to pass the Miller test in its depiction of corruption in ancient Rome, which dramatized the political theme that "absolute power corrupts absolutely".

Helen Mirren and John Gielgud star alongside one another in this movie. They have portrayed the same character, Hobson, in a Arthur related project: Gielgud played the character in Arthur (1981), for which he won an Oscar and had a cameo in its sequel Arthur 2: On the Rocks (1988), while Mirren played Hobson in Arthur (2011).

When a print of "Caligula" was sent to London for classification by the British Board of Film Censors, the UK government seized the copy on the grounds that it violated the Obscene Publications Act. Eight minutes of the most explicit footage were cut before it could be considered legally acceptable to screen the film. A further three minutes were removed to receive an X rating by the censors. It wasn't until 2008 that the uncut film could be legally available in the UK.

Spoilers

The trivia item below may give away important plot points.

In the original revised shooting script prepared by Tinto Brass and Malcolm McDowell, under the approval of Gore Vidal, Proculus was to have survived the film and later on become a major supporting character, but Bob Guccione and Franco Rossellini ordered them to re-instate his death scene back in the script. That particular draft of the shooting script is available on the three disc special edition DVD of the film.